The sporulation and germination-outgrowth developmental cycle of Bacillus subtilis provides a model biological system for examining intracellular differentiation. In view of the increasing evidence implication the aminoacyl-tRNA synthetases and tRNA in developmental processes, it is suggested that a study of their possible regulatory functions in this defined system should prove to be of major import. Specific areas of study will include: (1) An analysis to determine whether the lysyl-tRNA synthetase is modified or altered during sporulation and if so whether such a modification permits it to restrict the use of the isoaccepting tRNAlys species. (2) An examination of the roles of lysyl- and tryptophanyl -tRNA synthetases in regulating amino acid biosynthesis and protein turnover during spore outgrowth, vegetative growth and sporulation. (3) An examination of the effects of tRNA maturation mutants on the events in sporulation and spore outgrowth.